Prostaglandin H synthase (PGHS), which catalyzes the first reaction in the biosynthesis of prostaglandins and thromboxanes, plays a significant role in inflammation, reproduction, and possibly carcinogenesis. A second isoform of this enzyme (PGHS-2) is differentially regulated and has significantly different properties compared with those of PGHS-1. The long term objective of this project is to develop methods for large scale production and quantification of human PGHS-1 and PGHS-2. Methods for large scale production of human PGHS will be developed using cultured cells transfected with PGHS cDNA. Availability of large quantities of purified, metabolically active human PGHS isoforms will permit accelerated development of non-steroidal anti-inflammatory drugs (NSAIDs) that are selective for PGHS-2 relative to PGHS-1. Availability of immunoassays that distinguish PGHS-1 and PGHS-2, as well as PGHS promoter/reporter gene constructs, will permit differential quantitation of the levels of these two enzymes in platelets, leukocytes, and other clinical specimens and will accelerate research on the differential expression of PGHS isoforms in different disease states. These molecular probes can be used to monitor PGHS levels in individuals taking low dose aspirin based on its reported antithrombotic and/or anticancer activities. PROPOSED COMMERCIAL APPLICATION: Recombinant human PGHS-1 and PGHS-2 will be marketed to pharmaceutical companies for screening of NSAIDs selective for PGHS-2. Facile assays for PGHS-1 and PGHS-2 mRNA and protein levels, and promoter/reporter gene constructs of the genes are needed for evaluation of clinical specimens, and may prove to be invaluable tools for monitoring the pathology and pharmacological treatment of specific disease states including thrombosis, inflammation and cancer.